Nanoimprint technology in which a resin material formed on a substrate is embossed with an undulated pattern in nanometer size (1 to 1000 μm) (hereinafter, also referred to as “nanostructure(s)”) of a mold by pressing the two together has attracted attention recently. Applications of nanoimprint technology to optical materials, finer ICs, substrates for clinical laboratory test, and the like are now being developed and researched. Nanoimprint technology advantageously allows a component with a variety of characteristics to be produced at low costs as compared with conventional pattern-forming processes involving lithography and etching. This is because nanoimprinters have a simple configuration and are not so expensive than conventional apparatuses and further because it takes a short time to mass-produce components with the same shape.
Thermal nanoimprint and UV nanoimprint are known as nanoimprint technology. According to UV nanoimprint, for example, a mold with nanostructures is pressed against a UV-curable resin film formed on a transparent substrate, and the film is irradiated with UV ray, thereby producing a thin film with nanostructures in the inverse shape of the mold on the transparent substrate. Flat molds and batch process are commonly employed in UV nanoimprint, although it is still studied.
In order to mass-produce thin films with nanostructures at low costs by nanoimprint technology, roll-to-roll process is preferable to batch process. Roll-to-roll process allows continuous production of the thin film with nanostructures.
With respect to nanoimprint technology involving roll-to-roll process, for example, Patent Document 1 discloses that a pattern of a mold roller 52 is transferred onto a UV-curable resin coated on a mold roller 51 larger than the mold roller 52 while the pattern is extended by sequentially moving the mold roller 52 laterally as shown in FIG. 18. However, in this method, the mold roller 52 is moved, and so, the resulting film has a seam in the pattern. Thus this method is not suitably used for forming a nanopattern with a width larger than the width of the mold roller 52.
With respect to rollers used in roll-to-roll process in technologies other than nanoimprint technology, for example, Patent Documents 2 and 3 disclose a method of producing a roller with an undulated pattern directly formed thereon. When this method is applied to nanoimprint technology, however, a mold roller with nanostructures needs to be equipped with, for example, a bearing mechanism for coupling the mold roller with a nanoimprinter. This leads to an increase in costs on the mold roller, which is a problem in view of mass-production.
Further, for example, Patent Document 4 discloses, in FIG. 7, a method of attaching a cylindrical member with an undulated pattern to a roller. According to this method, however, it is difficult to form a continuous nanopattern by bending the member around the outer circumference of the roller, and as a result, the mold roller has a seam in the nanopattern.
In view of this, for example, Patent Documents 5 to 8 disclose, in a technology of producing optical materials with nanostructures, a method of using an aluminum substrate having a surface with nanosized cavities formed thereon by anodizing. In optical materials, “moth-eye structure (s)” is known as one type of the nanostructures. The moth-eye structures include, for example, conical protrusions in nanometer size formed on a transparent substrate surface. According to optical materials with the moth-eye structures, a reflected light amount can be dramatically decreased because a refractive index continuously changes from an air layer to a transparent substrate and so incident light does not recognize the air layer-transparent substrate interface as an optical surface.
According to this method involving anodizing, for example, as disclosed in FIG. 19 of Patent Document 8, nanosized recesses can be formed in a random placement and in a uniform distribution, and seamless nanostructures needed for continuous production can be formed on a columnar or cylindrical mold roller surface.
[Patent Document 1]
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